Widely known are technologies for estimating a three-dimensional positional relation between bones from a two-dimensional image obtained by capturing a joint with plain X-rays prior to surgery of osteoarthritis developing in a knee joint, a hip joint, and the like.
Japanese Patent Application Laid-open No. 2006-263241, for example, discloses a method for generating an evaluation function including relative fitness between a patient's skeleton and an implant component based on a computed tomography (CT) image or a magnetic resonance (MR) image. Japanese Patent Application Laid-open No. 2006-263241 also discloses a method for using the evaluation function to select an implant appropriate for the patient and make a surgical plan.
Actual human bones are subjected to muscle tension generated by a muscle attached to them, and the muscle tension changes stress acting on a joint. The conventional technology, however, does not estimate the stress with the acting force of the muscle taken into consideration, thereby failing to accurately calculate the stress acting on a joint of an actual patient.